Isolation of telomer acids



Un ted. States Patent 2,831,004 ISOLATION OF TELOMER ACIDS William S. Barnhart, Cranford, and Robert H. Wade, West Paterson, N. J., assignors, by mesne assignments, to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware No Drawing. Application March 15, 1956 Serial No. 571,588

Claims. (or. 260-408) to a drowning tank in which it is cooled and diluted with water to effect the separation of a product layer and a sulfuric acid layer. The cooling and dilution of the reaction mixture is conveniently etfected by the addition of ice thereto, with or without additional water, if desired.

The present invention relates to the specific method whereby the formation of two phases in the reaction mixture by the dilution thereof is effected. Prior to the present invention, the crude hydrolysis product was subjected to a prolonged extraction using an organic solvent, after which the organic phase or extract was washed with water, concentrated and distilled, and accordingly, this method involved the handling of large volumes of solution and was time consuming.

In accordance with the present invention, however, a simple, rapid and economical method of telomer acid isolation is provided since telomer acids, such as those disclosed in the aforementioned copending application, are insoluble in sulfuric acid having a concentration of about 30 to 70 percent by weight; hence, when a crude hydrolysis product is diluted with a sufiicient quantity of ice, or a mixture of ice and water, to lower the sulfuric acid concentration to a value within the range aforementioned, the formation of two phases results with the telomer acid separating as a lower phase and an aqueous sulfuric acid phase being the upper phase. It has been found that the optimum concentration of sulfuric acid for the separation of the two phases is about 50 percent by weight.

A crude telomer hydrolysis product may have the following weight distribution:

100% H so -between 100 and 135 lbs. or 125 lbs. Telomer-between l0 and 25 lbs. or 15 lbs. Telomer acid-between 90 and 120 lbs. or 100 lbs. ClSO H-between 15 and lbs. or 25 lbs. FSOJ-I-between 10 and 30 lbs. or 20 lbs. HCl-between 1 and 15 lbs. or'8 lbs. HF-between 0.5 and 2 lbs. or 1 lb.

The above mixture is obtained as a single phase when a telomer having less than 8 carbon atoms is hydrolyzed, but when higher molecular weight telomers, i. e., those having more than 8 carbon atoms, are hydrolyzed a two phase mixture is formed. The telomer acid product is distributed between the two phases, however, and, therefore, the two phases are treated as one. To this crude hydrolysis product is added between about 0.3 to 1 and about 20 to 1, preferably between about 0.5 to 1 and 2 to 1, volumes of ice to volume of product, and an equivalent volume is usually employed. The hydrolysis product then separates into two phases from which telomer acids can be removed conveniently. The upper aqueous sulfuric acid layer contains, in addition, HCl, HF and traces of telomer acid product. The traces of telomer acid may be removed from the upper phase by extraction with about 0.05 to 1, preferably 0.1 to 0.3, volume of solvent per volume of aqueous acid phase, suitable solvents being benzene, xylene, toluene, 1,1,2-trich1orotrifluoroethane, cyclohexane, carbon tetrachloride, or chlorobenzene, and the like.

The traces of telomer acid removed from the upper phase may then be added to the lower phase, or bottom layer, which contains unreacted telomer, telomer acid product, some sulfuric acid, and traces of HCl, HF, and water. The bottom layer or lower phase, is then subjected to washing with aqueous HSO or HCl to remove water soluble materials such as H and HF and also to maintain the telomer acid product in the organic phase of the two phases which are thus formed from the bottom layer. Water is then removed from the bottom layer by azeotropic distillation using toluene or benzene as an a'z'eotroping agent. The telomer acid product is then recovered by vacuum distillation.

In addition to the isolation of the acids disclosed in the aforementioned copending application, the present invention is also applicable to the isolation of other telomer acids which are formed by hydrolysis, certain of these acids being disclosed in copending applications Serial Nos. 463,073, filed October 18, 1954, and 493,554, filed March 10, 1955.

The invention will be further illustrated by reference to the following specific examples:

Example 1 A number of solubility tests were made to determine the solubility of various telomer acids in 50 weight percent sulfuric acid. The telomer acids tested were those prepared by the telomerization of chlorotrifluoroethylene using sulfuryl chloride as a telogen.

In the tests, 50 weight percent sulfuric acid was saturated with selected telomer acids and analyzed as shown below:

Mg. acid/ Weight Telomer Acid m1. percent solution Soluble O6 mono 0. 27 0. 019 a mono 0. 08 0. 006 C mono. 0. 2B 0. 020 C5 dlacid 0. 06 0. 005

Density of 50% H1804 is 1.395 gJml.

Example 2 Distillation data are given below: to 16, from a crude perchlorofluoroalkane hydrolysis prod- Percent Percent Fraction B. P., C. Moles Oonver- Yield slon CKCFr-CFCDAZI 90-110 3 mm 0. 45 Ol(CF-OFCl)s CFzOOOH 125-130/3 mm.. 3. 61 67 HOOG(cF:-CFC1)3 COOH 160-170/3 mm o. 95 19 21 The aqueous layer analyzed 60 weight percent sulfuric acid (d =l.70) and contained a total of 1.0 gram of telomer acid by analysis.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit thereof, and

the invention includes all such modifications.

We claim:

1. A method for the isolation of perchlorofluorocarboxylic acids from a crude perchlorofluoroalkane hydrolysis product containing sulfuric acid which comprises diluting the hydrolysis product to a concentration of about 30 to 70 percent by weight of sulfuric acid whereby an upper phase containing sulfuric acid and a lower phase containing said perchlorofluorocarboxylic acids are formed, and separating the phases.

2. A method according to claim 1 in which the crude hydrolysis mixture is diluted by the addition of ice.

3. A method for the isolation of a compound, having the formula in which n is an integer from 2 to 16, from a crude perchlorofluoroalkane hydrolysis product containing sulfuric acid which comprises diluting the hydrolysis product to a concentration of about 30 to 70 percent by weight of sulfuric acid whereby an upper phase containing sulfuric acid and a lower phase containing said compound having the formula: Cl(CF --CFCl) CF COOH are formed, and separating the phases.

4. A method according to claim 3 in which the crude hydrolysis mixture is diluted by the addition of ice.

5. A method for the isolation of a compound, having the formula in which Z is selected from the group consisting of carboxyl and perhalomethyl radicals having a total atomic weight not in excess of 146.5 and n is an integer from 2 1 s-Benzylthiuronium chloride precipitation of acids.

not containing sulfuric acid which comprises diluting the hydrolysis product to a concentration of about 30 to percent by weight of sulfuric acid whereby an upper phase containing sulfuric acidand a lower phase containing said compound having the formula:

are formed, and separating the phases.

6. A method according to claim 5 in which the crude hydrolysis mixture is diluted by the addition of ice.

7. A method for the isolation of a compound, having the formula in which Z is selected from the group consisting of carboxyl and perhalomethyl radicals having a total atomic weight not in excess of 146.5 and n is an integer from 2 to 16, from a crude perchlorofluoroalkane hydrolysis product containing sulfuric acid which comprises diluting the hydrolysis product to a concentration of about 30 to 70 percent by weight of sulfuric acid whereby upper phase containing sulfuric acid audia lower phase containing said compound having the formula:

are formed, and separating the phases.

8. A method according to claim 7 in which the crude hydrolysis mixture is diluted by the addition of ice.

9. A method for the isolation of perchlorofiuorocarboxylic acids, having from 4 to about 20 carbon atoms, from a perchlorofluoroalkane hydrolysis product containing sulfuric acid which comprises diluting the hydrolysis product to a concentration of about 30 to 70 percent by weight of sulfuric acid whereby an upper phase containing sulfuric acid and a lower phase containing said perchlorofluorocarboxylic acids are formed, and separating the phases.

10. A method according to claim 9 in which the hydrolysis product is diluted by the addition of ice.

No references cited. 

1. A METHOD FOR THE ISOLATION OF PERCHLOROFLUOROCARBOXYLIC ACIDS FROM A CRUDE PERCHLOROFLUOROALKANE HYDROLYSIS PRODUCT CONTAINING SULFURIC ACID WHICH COMPRISES DILUTING THE HYDROLYSIS PRODUCT TO A CONCENTRATION OF ABOUT 30 TO 70 PERCENT BY WEIGHT OF SULFURIC ACID WHEREBY AN UPPER PHASE CONTAINING SULFURIC ACID AND A LOWER PHASE CONTAINING SAID PERCHLOROFLUOROCARBOXYLIC ACIDS ARE FORMED, AND SEPARATING THE PHASES. 